1. Field of the Invention
This invention relates generally to apparatus and method for transferring a separated component in a liquid, and more particularly to apparatus and method for transferring or taking out a centrifugally separated component in a liquid such as blood contained in a blood bag.
2. Description of the Prior Art
In carrying out blood transfusion, recently, blood collected from a donor is centrifuged with a centrifugal separator for separating the collected blood into blood components, and then only the component required for a patient is transfused, in order to utilize the blood effectively and to reduce a burden on the patient who receives a blood transfusion. Owing to this component transfusion, it has become possible to utilize blood more effectively, as compared with the whole blood transfusion so far adopted.
In the above-mentioned component transfusion, connected bags (referred to as "multiple bag system") composed of a blood collecting bag and one or more bags are used.
As one of the multiple bag systems, there is known a triple bag system, which comprises a blood collecting bag, a platelet concentrate preserving bag (hereinafter, referred to as "PC bag") and a plasma preserving bag (hereinafter, referred to as "plasma bag") which are connected to each other through tubes. The blood collected into the blood collecting bag is centrifuged at least once to separate the blood into three components of erythrocyte concentrate, platelet concentrate, and platelet-poor plasma (hereinafter, referred to as "PRP method"), and the separated components are preserved in the blood bag, the PC bag and the plasma bag, respectively.
In the multiple blood bag system as described above, the respective bag is formed by laminating flexible polyvinyl chloride sheets and further fusing the periphery thereof. The reasons why the flexible polyvinyl chloride is used is that this material has an appropriate gas penetrability, and further that this material is excellent in preservation of cells such as erythrocyte, platelet. etc., in heat-resistance in autoclave sterilization, and in flexibility endurable to centrifugal separation and suitable for shake preservation. Further, the material is also low in manufacturing cost.
The blood collected into a blood collecting bag is centrifuged by placing the blood collecting bag in a centrifugal cup formed of a hard material and formed into a cup-shaped container and mounting the centrifugal cup with the blood collecting bag to a centrifugal separator. Further, the separated components are collected in accordance with the following steps, that is, first the blood collecting bag is removed from the centrifugal cup; the blood collecting bag is then set to an automatic separating stand; and thereafter the blood collecting bag is pressed, so that the supernatant plasma layer is discharged. As the automatic separating stand, for example, one disclosed in U.S. Pat. No. 4,976,851 can be used.
In the method as described above, however, after the centrifugal separation, the following operations are required, that is, the blood collecting bag is removed from the centrifugal cup, the removed bag is then transferred to the separating stand, and thereafter the bag is set to the separating stand. Therefore, there are various problems in that the blood collecting bag is shaken or vibrated during the above-mentioned operations and further the bag is likely to be deformed because of its flexibility. With this result, the interfaces between the respective two layers of the three separated components are likely to be disturbed during the operations, thus leading to the problem that yield (quantity of collection or purity) of each of the separated components is deteriorated. When the yield of each of the separated components is lowered as described above, the quality of blood products is also degraded, and therefore there exists such a case that the blood collecting bag must be centrifuged again as occasion demands.
In addition, since it takes a long time to take out the blood collecting bag from the centrifugal cup and further to set the bag to the separating stand. In particular, if these operations are carried out carefully so as not to disturb the interfaces between the respective separated components, a further long time is required.